1. Field of the Invention
The present invention relates to a fire retardance-imparting additive. More particularly, it relates to a fire retardance-imparting additive that can impart an excellent retardance.
2. Description of the Related Art
Thermoplastic resins are used in various fields such as the fields of automobile parts, household appliance parts, office automation appliance parts, etc. because they are excellent in not only moldability but also impact resistance, but they have limited use because of their high flammability.
As a method for imparting fire retardance to a thermoplastic resin, the addition of a halogen-containing, phosphorus-containing or inorganic fire retardant to the thermoplastic resin is known and it achieves a certain extent of fire retardance. However, in recent years, the need for thermoplastic resins to be safe in the presence of fire has been suddenly highlighted, and there has been an eager desire for the development of an improved technique for imparting fire retardance which does not also create environmental problems and does not deteriorate the resin""s mechanical properties.
On the other hand, there are known compositions containing a substituted aromatic vinyl resin having inorganic acid salt groups as the substituents on the aromatic rings, such as polystyrene sulfonic acid salts. For example, there are known a process for producing a stabilized resin from a polystyrene sulfonic acid sodium salt and a polyvinyl chloride (JP-A-7-268028), a process for producing a stabilized resin from a polystyrene sulfonic acid sodium salt and a polyolefin (JP-A-6-248013), a thermal printing paper containing a polystyrene sulfonic acid alkanolamine salt (JP-A-2-136285), a thermal recording material comprising an acrylic emulsion containing a polystyrene sulfonic acid salt (JP-A-2-69283), a thermo-setting resin comprising a polystyrene sulfonic acid salt and a methylol-group-containing polystyrene (JP-A-1-294729), a thermal recording material comprising a polystyrene sulfonic acid salt (JP-A-6-3312883 and JP-A-1-8090), a material for organic semiconductor comprising a polystyrene sulfonic acid salt (JP-A-6-3215722), an antistatic polyester film comprising a polystyrene sulfonic acid sodium salt (JP-A-6-141525), microcapsules for pressure-sensitive copying paper which contain a polystyrene sulfonic acid salt (German Patent Nos. 3232811 and 3037309), a heat-resistant resin comprising a polystyrene/polyphenylene oxide alloy (Proceedings of the 6th Sony Research Forum p. 552 (1996)), the miscibility of a polymer system obtained by introducing a sulfonate into polystyrene/polyphenylene oxide (Polymer, Vol. 33, Nr6, 1210 (1992)), etc. Such compositions, however, are different in make-up from the fire retardance-imparting additive of the present invention, and a use of a specific polystyrene sulfonic acid salt as a fire retardance-imparting additive has not been known.
In view of such conditions, the present invention is intended to provide a fire retardance-imparting additive free from the above problems, namely, an excellent fire retardance-imparting additive.
The present inventors earnestly investigated the fire retardance of thermoplastic resins and consequently found that surprisingly, the addition of an aromatic vinyl resin having specific substituents to a thermoplastic resin greatly improves the fire retardance, whereby the present invention has been accomplished.
That is, the present invention provides a fire retardance-imparting additive that comprises a substituted aromatic vinyl resin having acid salt groups as the substituents on the aromatic rings and comprises a structure represented by the following formula 1: 
wherein X is an acid salt group, m is 1 to 5, Y is a hydrogen atom or a hydrocarbon group of 1 to 10 carbon atoms, and n is a molar fraction chosen in a range of 0 less than nxe2x89xa61.